LibC: Add sys/auxv.h with getauxval

userspace/libraries/LibC/sys/auxv.cpp

@@ -0,0 +1,40 @@
+#include <sys/auxv.h>
+#include <unistd.h>
+
+#include <kernel/API/SharedPage.h>
+
+struct auxv
+{
+	unsigned long a_type;
+	unsigned long a_val;
+};
+
+static const auxv* s_auxv = nullptr;
+
+volatile Kernel::API::SharedPage* g_shared_page = nullptr;
+
+__attribute__((constructor(101)))
+static void _init_auxv()
+{
+	if (environ == nullptr)
+		return;
+
+	const char* const* null_env = environ;
+	while (*null_env)
+		null_env++;
+
+	s_auxv = reinterpret_cast<const auxv*>(null_env + 1);
+
+	if (auto value = getauxval(AT_SHARED_PAGE))
+		g_shared_page = reinterpret_cast<volatile Kernel::API::SharedPage*>(value);
+}
+
+unsigned long getauxval(unsigned long type)
+{
+	if (s_auxv == nullptr)
+		return 0;
+	for (const auxv* aux = s_auxv; aux->a_type != AT_NULL; aux++)
+		if (aux->a_type == type)
+			return aux->a_val;
+	return 0;
+}